Hybrid car and dynamo-electric machine

ABSTRACT

A hybrid drive type vehicle having a permanent magnet type synchronous motor can provide high torque characteristics in low revolution speed range of the engine and high power generation characteristics at high revolution speed range of the engine. The hybrid drive type vehicle includes an electric rotary machine being formed with a stator and a rotor. A field magnet of the rotor include a first field magnet and a second field magnet. The first and second field magnets are opposing with a magnetic pole of the stator and having a mechanism for varying a phase of a magnetic pole resulting from combination of the first and second field magnets relative to the magnetic pole of the first field magnet depending upon direction of a torque of the rotor.

This application is a divisional of application Ser. No. 09/654,081,filed Sep. 1, 2000.

BACKGROUND OF THE INVENTION

The present invention relates generally to a hybrid-type electricvehicle. More particularly, the invention relates to an electric rotarymachine for driving the hybrid drive type vehicle and generating anelectric power, and a control method therefor. Further particularly, theinvention relates to an electric rotary machine, in which a rotor of theelectric rotary machine is constructed with a first field magnet and asecond field magnet, and which is variable of effective flex amountdepending upon a direction of torque.

DESCRIPTION OF THE RELATED ART

As a conventional hybrid drive type vehicle, there are (1) a serieshybrid type driving a generator by an output torque of an engine as aninternal combustion engine for obtaining an electric power and driving aelectric rotary machine connected to a wheel axle by the electric powerfor driving a vehicle by a driving torque generated by the electricrotary machine, and (2) a parallel hybrid type, in which a part of theoutput torque of the engine is converted into an electric power andremaining output torque is transmitted to the wheel axle as drivingtorque for driving the vehicle by a driving torque of the electricrotary machine using the generated electric power and the wheel axledriving torque of the engine.

In the recent trend, in view point of sizes and costs for the motorand/or battery, attention is attracted to (2) the parallel hybriddriving type vehicle. For example, as disclosed in Japanese PatentApplication Laid-Open No. 9-132042 (1997), a parallel hybrid drive typevehicle of the type wherein the engine and two electric rotary machinesare connected to respective shafts of a planetary gear mechanism and adriving force is distributed depending upon load and revolution speed ofthe engine and respective electric rotary machines (this type will behereinafter referred to as “two motor system”), has already marketed.

However, such prior art requires two electric rotary machines and twoinverter circuits for driving the electric rotary machines and newlyarranging the planetary gear mechanism and thus requires significantreconstruction of the vehicle to cause significant increase of the costassociating therewith.

Therefore, as shown in Japanese Patent Application Laid-Open No.7-298696 (1995), there has been proposed a system, in which an electricrotary machine is directly connected to a crankshaft of the engine forswitching driving mode and generating mode in one electric rotarymachine (this system will be referred to as “single motor system”). Thissingle electric rotary machine system is advantageous in view point ofcost and capability of add-on the existing vehicle.

In both of single motor system and two motor system, as the electricrotary machine, a permanent magnet field type electric rotary machinearranged a permanent magnet on a rotor or a squirrel cage inductionelectric rotary machine, in which a secondary conductors made ofaluminum alloy or copper alloy are arranged on the rotor in cage-likefashion, may be employed.

As set forth above, the single motor system is more advantageous thanthe two motor systems in viewpoint of the cost. However, the followingconstraints are present even in the single motor system.

(1) It has to be achieved both of a high torque characteristics in lowrevolution speed range upon starting-up of the engine and high-powergeneration characteristics in high revolution speed range.

(2) A revolution speed to generate a torque (maximum torque to begenerated by the motor) upon starting-up of the engine is less than orequal to one tenth for a motor revolution speed at the allowable maximumrevolution speed of the engine.

(3) The present invention is directed to the electric rotary machinemounted on the vehicle, and as a power source, a battery charging anddischarging within a voltage variation range centered at a certainvoltage, is employed. Therefore, if a voltage far beyond a chargingvoltage of the battery is charged, it is possible to damage the batteryin the worst case.

SUMMARY OF THE INVENTION

The present invention has been worked out in view of the shortcoming inthe prior art as set forth above. It is therefore an object to provide ahybrid drive type vehicle having a permanent magnet type synchronousmotor obtainable of high torque characteristics in low revolution speedrange of the engine and high power generation characteristics at highrevolution speed range of the engine.

According to one aspect of the present invention, a hybrid drive typevehicle comprises:

an internal combustion engine driving a vehicle;

a battery charging and discharging an electric power;

an electric rotary machine mechanically connected with a crankshaft ofthe internal combustion engine for starting up the internal combustionengine as driven by the electric power supplied from the battery, anddriven by revolution of the internal combustion engine for performinggeneration for charging the battery;

an inverter for controlling driving and generating of the electricrotary machine;

a controller controlling the inverter;

revolution speed detecting means for detecting a revolution speed of theinternal combustion engine or the electric rotary machine;

the electric rotary machine being formed with a stator having a primarywinding and a rotor having a field magnet, the field magnet beingconstituted of a first field magnet alternately arranged mutuallyopposite magnetic poles in sequentially in circumferential direction anda second field magnet capable of causing relative angular displacementrelative to the first field magnet and alternately arranged mutuallyopposite magnetic poles in sequentially in circumferential direction,the first and second field magnets being opposing with a magnetic poleof the stator and having a mechanism for varying a phase of a magneticpole resulting from combination of the first and second field magnetsrelative to the magnetic pole of the first field magnet depending upondirection of a torque of the rotor,

the mechanism for varying the magnetic pole depending upon the directionof the torque including means for aligning centers of the same magneticpoles of the first and second field magnets by balance between torquedirection generated in the rotor and magnetic action between the firstand second magnetic and means for causing offset of the center of thesame magnet poles of the first and second field magnetic associatingwith generation of the torque generated in the rotor in the oppositedirection.

Operation of one aspect of the invention as set forth above will bediscussed.

In FIG. 6, the characteristics of an effective flux relative to arotational angular velocity of the permanent magnet type synchronouselectric rotary machine, an induced electromotive force, and a terminalvoltage are shown.

An induced electromotive force E₀ of the permanent magnet typesynchronous electric rotary machine is determined by a constant magneticflux Φ generated by the permanent magnet and rotational angular velocityω of the electric rotary machine. Namely, as shown in FIG. 6, when therotational angular velocity ω of the electric rotary machine (revolutionspeed) is increased, the induced electromotive force E₀ of the electricrotary machine is proportionally increased. However, as an essentialcondition in mounting on the vehicle is charging of the battery. Inorder to charge the battery, the induced electromotive force to begenerated in the electric rotary machine has to be suppressed to belower than or equal to a battery charge voltage so as not to damage thebattery. Therefore, in the permanent magnet type synchronous electricrotary machine, it requires to perform weakening field control forreducing magnetic flux generated by the permanent magnet in range of therevolution speed higher than or equal to a predetermined value.

Since the induced electromotive force is increased in proportion to therotational angular velocity, current for weakening field control has tobe increased. Therefore, a large current has to flow through the coil asthe primary winding to inherently cause heating of the coil. Therefore,efficiency of the electric rotary machine is lowered in the highrevolution speed range to possibly cause demagnetization or so forth ofthe permanent magnet due to heating beyond cooling capacity.

Therefore, according to one aspect of the present invention, the firstfield magnet and the second field magnet of the rotor of the electricrotary machine are arranged coaxially for varying the centers of themagnetic poles of the first and second field magnets depending upon thedirection of the rotational torque so that the centers of the samemagnetic poles of the first and second field magnets are aligned uponserving as an electric motor in the low revolution speed range, such asupon starting up of the engine or the like to provide large effectiveflux amount by the permanent magnet opposing to the magnetic poles ofthe stator to attain high torque. Next, upon serving as the generator,when the rotating direction of the rotor is the same, the torque to beapplied to the rotor becomes opposite to that applied upon serving asthe electric motor to cause offset of the centers of the same magneticpoles of the first and second field magnets to reduce effective fluxamount by the permanent magnet opposing the magnetic poles of the statorto attain weakening field effect to obtain high power generationcharacteristics in high revolution speed range.

In the preferred construction, the electric rotary machine serves as anelectric motor at low revolution speed range and having means foraligning centers of the same magnetic poles of the first and secondfield magnets by balance between torque direction generated in the rotorand magnetic action between the first and second magnetic, and serves asa generator at high revolution speed range and having means for causingoffset of the center of the same magnet poles of the first and secondfield magnetic associating with generation of the torque generated inthe rotor in the opposite direction. Also, the electric rotary machineserves as an electric motor at low revolution speed range and havingmeans for aligning the first and second field magnets at an initialposition by balance between torque direction generated in the rotor andmagnetic action between the first and second magnetic, and serves as agenerator at high revolution speed range and having means for causingoffset of the center of the same magnet poles of the first and secondfield magnetic associating with generation of the torque generated inthe rotor in the opposite direction, and the mechanism for varying thecenter of the magnetic pole associating with variation of the torquedirection is constructed by rigidly securing the first magnet on a shaftand separating the second field magnet from the shaft, and the shaft andthe second field magnet are permitted to cause relative angular offsetwithin an angular range corresponding to circumferential length of onemagnetic pole for causing offset of the center of the poles of the firstfield magnet and the center of the poles of the second field magnet. Astopper may be provided at a position away from the side surface of thesecond field magnet. A serve mechanism may be provided for displacingthe stopper in parallel to the shaft depending upon revolution speed.

According to another aspect of the present invention, an electric rotarymachine comprises:

a stator having a primary winding and a rotor having a field magnet, thefield magnet being constituted of a first field magnet alternatelyarranged mutually opposite magnetic poles in sequentially incircumferential direction and a second field magnet capable of causingrelative angular displacement relative to the first field magnet andalternately arranged mutually opposite magnetic poles in sequentially incircumferential direction, the first and second field magnets beingopposing with a magnetic pole of the stator and having a mechanism forvarying a phase of a magnetic pole resulting from combination of thefirst and second field magnets relative to the magnetic pole of thefirst field magnet depending upon direction of a torque of the rotor,

the mechanism for varying the magnetic pole depending upon the directionof the torque including means for aligning centers of the same magneticpoles of the first and second field magnets by balance between torquedirection generated in the rotor and magnetic action between the firstand second magnetic and means for causing offset of the center of thesame magnet poles of the first and second field magnetic associatingwith generation of the torque generated in the rotor in the oppositedirection.

The mechanism for varying the center of the magnetic pole associatingwith variation of the torque direction may be constructed by rigidlysecuring the first magnet on a shaft and separating the second fieldmagnet from the shaft, and the shaft is formed with a threaded portionserving as a bolt and an inner periphery of the second field magnetbeing formed with a thread for serving as a nut for connection in threadengagement, and a stopper is provided at a position away from the sidesurface of the second field magnet, and a serve mechanism for displacingthe stopper in parallel to the shaft depending upon revolution speed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings of thepreferred embodiment of the present invention, which, however, shouldnot be taken to be limitative to the invention, but are for explanationand understanding only.

In the drawings:

FIG. 1A is a perspective view showing a layout of an electric rotarymachine and an engine in the preferred embodiment of a hybrid drive typevehicle according to the present invention;

FIG. 1B is a schematic block diagram showing connection between theengine and the electric rotary machine;

FIG. 2 is a diagrammatic illustration showing a case where a center ofthe same pole of the rotor of the electric rotary machine of FIG. 1 isoffset;

FIG. 3 is a diagrammatic illustration showing a case where a center ofthe same pole of the rotor of the electric rotary machine of FIG. 1 isaligned;

FIG. 4 is a block diagram showing a power source system of the electricrotary machine of FIG. 1;

FIG. 5 is a block diagram showing a control system of the electricrotary machine of FIG. 1;

FIG. 6 is a chart showing variation characteristics relative torotational angular velocity of the electric rotary machine of FIG. 1;

FIG. 7 is an illustration showing another embodiment of the electricrotary machine according to the present invention;

FIG. 8 is a general illustration of a rotor of the electric rotarymachine of FIG. 7;

FIG. 9A is a perspective view showing a layout of an electric rotarymachine and an engine in another embodiment of a hybrid drive typevehicle according to the present invention;

FIG. 9B is a schematic block diagram showing connection between theengine and the electric rotary machine; and

FIG. 10 is a general illustration of a rotor of the electric rotarymachine of another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be discussed hereinafter in detail in termsof the preferred embodiment of the present invention with reference tothe accompanying drawings. In the following description, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be obvious, however, tothose skilled in the art that the present invention may be practicedwithout these specific details. In other instance, well-known structureare not shown in detail in order to avoid unnecessary obscurity of thepresent invention.

FIGS. 1A and 1B show a layout of the preferred embodiment of a permanentmagnet type synchronous electric rotary machine (direct connection type)according to the present invention. The preferred embodiment of apermanent magnet type synchronous electric rotary machine 2 is arrangedbetween an engine 1 as an internal combustion engine for generating adriving force of a vehicle and a power transmission 3 of the vehicle. Acrankshaft (not shown) of the engine 1 and a shaft (shaft 22 of a rotorin FIG. 2) of the permanent magnet type synchronous electric rotarymachine 2 are connected directly or mechanically via a speed changerconstructed by a planetary gear speed reducer.

On the other hand, the shaft of the permanent magnet type synchronouselectric rotary machine 2 and an input shaft of the power transmission 3are directly connected via a clutch (not shown) or a torque converter(not shown) as a fluid coupling shutting off a driving force.

By constructing as set forth above, by operating the clutch or torqueconverter, the shown embodiment of the permanent magnetic typesynchronous electric rotary machine 2 can start-up the engine 1. Afterstarting up the engine 1, by operating the clutch and the torqueconverter, a driving force of the engine 1 can be transmitted to theinput shaft of the power transmission 3. In conjunction therewith,driving forces of the engine 1 and the permanent magnet type synchronouselectric rotary machine 2 are transmitted to the input shaft of thepower transmission 3.

On the other hand, the permanent magnet type synchronous electric rotarymachine 2 is electrically connected to a battery 5 via an inverter 4 forserving as an electric motor as assisting starting up of the engine 1.

Upon power generation, an electric force generated in the permanentmagnet type synchronous electric rotary machine 2 is converted into adirect current by the inverter 4 for charging the battery 5.

FIG. 2 shows general construction showing the case where a center of thesame pole of the rotor of the electric rotary machine of FIG. 1 isoffset. On an iron core 10 of a stator, armature coils 11 are coiledwithin slots. The iron core 10 of the stator is shrink-fitted in ahousing 13 which is formed with a cooling water passage 12 for flowing acooling water therein. Here, securing method of the stator iron core 10and the housing 13 is not limited to shrink-fitting but can be pressurefitting or so forth.

A permanent magnet embedded type rotor 20 is formed with a first rotor20A fixed on the shaft 22 and a second rotor 20B separated from theshaft 22. Of course, the rotor can be not only the permanent magnetembedded type rotor but also a surface magnet type rotor.

On the first rotor 20A, permanent magnets 21A having magnetic poles ofalternate polarities are arranged in circumferential direction.Similarly, on the second rotor 20B, permanent magnets 21B havingmagnetic poles of alternate polarities are arranged in circumferentialdirection. Field magnets of the first and second rotors are opposed tomagnetic poles of the stator.

Inner periphery of the second rotor 20B is threaded to form a nut, and acorresponding portion of the shaft is also threaded to form a bolt forpermitting mutual engagement between the second rotor 20B and the shaftby thread engagement.

On the other hand, for preventing the second rotor 20B from offsettingbeyond a predetermined displacement magnitude from the center of thestator, a stopper 24 is provided at a position away from a side surfaceof the second rotor 20B. Furthermore, a stopper driving actuator 25serving a servo mechanism is provided for shifting the stopper 24 inaxial direction in parallel to the shaft for controlling effective fluxamount depending upon rotation speed.

By constructing as set forth above, the effective magnetic flux amountof the permanent magnet can be varied depending upon direction of thetorque.

Basically, in the electric rotary machine having the armature coil onthe stator and the permanent magnet on the rotor, when the rotatingdirection of the rotor is the same either upon acting as the electricmotor or as the generator, torques to be applied to the rotor is in theopposite direction upon acting as the electric motor or as thegenerator.

When the basic theory set forth above is applied to the preferredembodiment of the electric rotary machine according to the presentinvention, the following effects can be obtained.

When the electric rotary machine is operated as the electric motor atlow revolution speed range, such as starting up of the engine or thelike, the centers of the same magnetic pole of the first rotor 20A andthe second rotor 20B are aligned to make the effective flux amount ofthe permanent magnet opposing the magnetic pole of the stator maximum toobtain high torque characteristics, as shown in FIG. 3.

Next, upon acting as the generator, when the rotating directions of therotors are the same, directions of the torques to be applied to therotors are opposite to the case acting as the electric motor. Then thesecond rotor 20B is rotated relative to the shaft 22 in looseningdirection to move away from the first rotor 20A to widen a distancebetween the first rotor 20A and the second rotor 20B to cause offset ofthe center of the same poles to reduce effective flux amount of thepermanent magnet opposing the magnetic pole of the stator. Thus, fieldweakening effect can be achieved to obtain high power generationcharacteristics in the high revolution speed range.

FIG. 4 is a block diagram of a power source system of the electricrotary machine of FIG. 1.

Three-phase terminal of the permanent magnet type synchronous electricrotary machine 2 mechanically connected to the engine 1, is electricallyconnected to the inverter 4. A direct current side terminal of theinverter 4 is connected to the battery 5 and to other high voltagesystem. On the other hand, in the shown embodiment, low voltage systemfor a head lamp, audio and so forth is provided. Power supply for thelow voltage system is performed by lowering the voltage from the highvoltage system by DC—DC converter 30 for supplying to a low voltagebattery 9 and other low voltage drive devices (head lamp, audio and soforth). Depending upon drive mode of the vehicle, the permanent magnetictype synchronous electric rotary machine 2 is switched between drivingmode and generating mode. Switching of mode and supplying of a commandvalue to the permanent magnet type synchronous electric rotary machine 2is performed by performing arithmetic operation and judgment by acontroller 11 for outputting the command value to the inverter 4 forcontrolling the permanent magnet type synchronous electric rotarymachine 2. On the other hand, a controller 31 performs cooperativecontrol of the permanent magnet type synchronous electric rotary machine2 and the engine 1 by making the command value output to the inverter 4common with an engine controller 32 controlling a throttle valve opendegree, fuel injection amount and so forth of the engine throughcommunication, direct memory access or so forth.

Next, discussion will be given for control performed in the controller31.

FIG. 5 is a block diagram showing a control system for the electricrotary machine of FIG. 1.

At first, on the basis of information (battery remaining capacity, drivemode, throttle valve open degree and so forth) from the enginecontroller (32 of FIG. 4) and independently installed sensor andrevolution speed of the permanent magnet type synchronous electricrotary machine 2, a driving condition judging portion 201 makes judgmentof driving operation of the permanent magnet type synchronous electricrotary machine 2 to output a current command value. The current commandvalue output from the driving condition judging portion 201 is input toa current control block 203 performing anti-interference control or soforth with reference to a difference with an instantaneous current valueof the permanent magnet type synchronous electric rotary machine 2through a PID compensation block 202.

Output of the current control block 203 is converted into a three-phasealternating current to control the permanent magnet type synchronouselectric rotary machine 2 via the inverter. On the other hand, thecurrents of respective phases (currents of at least two phases) of thepermanent magnet type synchronous electric rotary machine 2 andrevolution speed (or engine revolution speed, or in the alternative,multiplied value of the engine revolution speed) are detected. Thecurrent in each phase is converted into a biaxial current by a biaxialconverter block 205 for feeding back to the current command value. Onthe other hand, the revolution speed is input to the driving conditionjudging portion 201 to be information for judgment of driving condition.

FIG. 7 shows another embodiment of the electric rotary machine accordingto the present invention.

The shown embodiment is characterized by a mechanism permitting angulardisplacement of the second rotor for angle θ instead of providing thethread 23 in the second rotor shown in FIG. 2.

FIG. 8 is general illustration of the rotor of the electric rotarymachine of FIG. 7.

In place of the threaded portion of the second rotor shown in FIG. 2, agear teeth like toothing is provided on the shaft 22 and complementarytoothing is formed on the inner periphery of the second rotor 20B forengagement with the shaft. The pitch of the teeth is greater than thewidth of the teeth so that the shaft inserted into the second rotor 20Bis permitted to cause relative angular displacement for thepredetermined angle θ. Furthermore, by disposing a spring 26 and adumper 27 between mating teeth and groove for damping abrupt collision.

FIG. 9 shows a layout of the electric rotary machine and the engine ofanother embodiment of the present invention (transverse type). Theengine 1 and the permanent magnet type synchronous electric rotarymachine 2 are connected by a metal belt 7 wound around a crank pulley 6and a pulley 8 rigidly secured on the shaft of the permanent magnet typesynchronous electric rotary machine 2. It should be appreciated that thecrank pulley 6 and the pulley 8 may also be connected by a chain, coggedbelt and the like. Also, in place of the crank pulley 6 and the pulley8, a gear may also be used.

Advantage of the construction as illustrated in FIG. 9 is presence of aspeed change mechanism having a speed ratio between the engine 1 and thepermanent magnet type synchronous electric rotary machine 2 by the crankpulley 6, the metal belt 7 and the pulley 8 interposed between theengine 1 and the permanent magnet type synchronous electric rotarymachine 2. For example, by setting the radius ratio of the crank pulley6 and the pulley 8 at 2:1, the permanent magnet type synchronouselectric rotary machine 2 is driven at a speed double of the engine 1.Associating with this, upon starting up of the engine 1, the permanentmagnet type synchronous electric rotary machine 2 is required togenerate a half of the torque required for starting up of the engine 1.Therefore, it becomes possible to form the permanent magnet typesynchronous electric rotary machine 2 compact. Other electricalconnection and function are the same as those discussed in connectionwith FIG. 5.

The permanent magnet type synchronous electric rotary machine accordingto the present invention is constructed by dividing the rotor into thefirst field magnet and the second field magnet arranged coaxially andfor varying the center of the magnetic poles of the first and secondfield magnets to vary the effective flux amount by the permanent magnetopposing to the stator magnetic pole.

Although the present invention has been illustrated and described withrespect to exemplary embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omission and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodied within a scope encompassed andequivalent thereof with respect to the feature set out in the appendedclaims.

For instance, while the foregoing discussion has been given for thepermanent magnet type synchronous electric rotary machine having fourmagnets, the present invention is applicable for the electric rotarymachine having two or six magnets. For example, FIG. 10 shows the casewhere the present invention is applied for the permanent magnet typesynchronous electric rotary machine having eight magnets. Needless tosay, the rotor may be either embedded magnet type or surface magnettype.

What is claimed is:
 1. A hybrid vehicle comprising: an internalcombustion engine; a battery which stores and discharges electric power;an electric rotary machine mechanically connected with a crankshaft ofsaid internal combustion engine for starting up said internal combustionengine by the electric power supplied from said battery, and generatingan electric power by revolution of said internal combustion engine tocharge said battery; an inverter for controlling driving and generatingof said electric rotary machine; and a controller for controlling saidinverter; wherein said electric rotary machine is formed with a statorhaving a winding and a rotor rotatably disposed and separated from saidstator by a gap; said rotor is divided along the direction of the axisof rotation into two-piece parts; said two rotor piece parts haverespective field magnets whose polarities differ from each other, andare alternately arranged mutually with respect to a direction ofrotation; one of said two rotor piece parts has a mechanism for varyinga relative rotation-axis directional position with respect to the otherof said two rotor piece parts, depending on an equilibrium of a magneticinteraction force between the field magnet of one of said two rotorpiece parts and the field magnet of the other of said two rotor pieceparts and a torque direction of the rotor.
 2. The hybrid vehicleaccording to claim 1, wherein: during low speed rotation of saidelectric rotary machine, equilibrium of the magnetic interaction forcebetween the field magnet of one of said two rotor piece parts and thefield magnet of the other of said two rotor piece parts and the torquedirection of the rotor is made and a magnetic pole center of one of saidfield magnets of said two rotor piece parts is caused to align with amagnetic pole center of the other of said field magnets of said tworotor piece parts, so that said electric rotary machine operates as anelectric motor; and during high speed rotation of said electric rotarymachine, the direction of torque generated in the rotors is madeopposite to that of said electric motor and the magnetic pole center ofone of said field magnets of said two rotor piece parts is caused toshift with respect to the magnetic pole center of the other of saidfield magnets of said two rotor piece parts, so that said electricrotary machine operates as an electric generator.
 3. The hybrid vehicleof claim 1, wherein said mechanism by varying a relative rotation axisdirection position changes the relative rotation axis direction positionof one of said two rotor piece parts with respect to the other of saidtwo rotor piece parts within an angle corresponding to one magneticpole.
 4. The hybrid vehicle according to claim 1, wherein said mechanismfor varying a relative rotation axis direction position comprises ascrew mechanism including a bolt mechanism provided on a shaft on whichthe other of said two rotor piece parts is fixed and a nut mechanismprovided on one of said two rotor piece parts.
 5. The hybrid vehicleaccording to claim 1, further comprising: a stopper on the side of oneof said two rotor piece parts which is opposite to a side of the otherof said two-rotor piece parts, for supporting one of said two rotorpiece parts from its side; and a servo mechanism for changing a rotationaxis direction position of said stopper depending on the rotation speedsaid rotor.
 6. The hybrid vehicle according to claim 3, furthercomprising: a stopper on the side of one of said two rotor piece partswhich is opposite to the side of the other of said two rotor pieceparts, for supporting one of said two rotor piece parts from its side;and a servo mechanism for changing the rotation axis direction positionof said stopper depending on rotation speed said rotor.
 7. The hybridvehicle according to claim 4, further comprising: a stopper on the sideof one of said two rotor piece parts which is opposite to the side ofthe other of said two rotor piece parts, for supporting one of said tworotor piece parts from is side; and a servo mechanism for changing therotation axis direction position of said stopper depending on therotation speed said rotor.
 8. An electric rotary machine comprising: astator having a winding; and a rotor rotatably disposed and separatedfrom said stator by a gap, said rotor being divided into two rotor pieceparts along an axis of rotation, said two rotor piece parts havingrespective field magnets whose polarities differ from each other, andare alternately arranged mutually with respect to a direction of therotation, one of said two rotor piece parts having a mechanism forvarying a relative rotation-axis directional position with respect tothe other of said two rotor piece parts, depending on equilibrium of amagnetic interaction force between the field magnet of one of said tworotor piece parts and the field magnet of the other of said two rotorpiece parts and a torque direction of the rotor.
 9. An electric rotarymachine according to claim 8, wherein said mechanism for varying arelative rotation axis direction position changes the relative rotationaxis direction position of one of said two rotor piece parts withrespect to the other of said two rotor piece parts within an anglecorresponding to one magnetic pole.
 10. An electric rotary machineaccording to claim 8, wherein said mechanism for varying a relativerotation axis direction position comprises a screw mechanism thatincludes a bolt mechanism provided on a shaft on which the other of saidtwo rotor piece parts is fixed and a nut mechanism provided on one ofsaid two rotor piece parts.
 11. An electric rotary machine according toclaim 8, further comprising: a stopper on the side of the one of saidtwo rotor piece parts which is opposite to the side of the other of saidtwo rotor piece parts for supporting one of said two rotor piece partsfrom its side; and a servo mechanism for changing the rotation axisdirection position of said stopper depending on rotation speed saidrotor.